The invention relates to a micro-mechanical coupling having a coupling receiver and a coupling counterpart, which is held in a receiving depression of the coupling receiver. The invention moreover relates to a process for manufacturing such a coupling.
From xe2x80x9cPlug-in Connectors for SMT,xe2x80x9d SMT International Conference (Products-Manufacture-Processing), page 222, Hubert A. Holzmann (1987), a micro-mechanical coupling of the type mentioned at the outset is already known where, as coupling receiver, a printed circuit is provided which is penetrated transversely to its plate level by a receiver depression, into which a pointed press-in pin is inserted. The coupling counterpart forms, together with the receiver depression, a press fit which fixes the coupling counterpart in the coupling receiver in a friction-locking manner. This previously known coupling has the disadvantage that the press fit brings about tensile stress in the coupling receiver which diminishes the mechanical strength of the coupling receiver. The formation of cracks can even occur in the area of the press fit in the coupling receiver.
From the book Micromechanics by Anton Heuberger, page 456, Springer-Verlag (1989), a coupling of the type mentioned at the outset is already known, where the coupling receiver is a semiconductor chip having a large number of V-shaped receiver depressions on one of its surfaces, which run respectively along a straight line on the surface of the semiconductor chip. Into the-respective V-shaped receiver depressions, in the direction of travel of the receiver depression, an end region of a fiber-like optical conductor is installed. The coupling is constructed as a transceiver array, and has on the one hand receiver conductors, the ends of which are arranged adjacent to the optical receiving elements situated on the semiconductor chip, and on the other hand has coupling transmitter conductors, the ends of which are arranged adjacent to optical transmitting elements situated on the semiconductor chips, which are connected with the receiving elements through an amplifier and drive unit.
This previously known coupling has the disadvantage that the V-shaped receiver depressions occupy a not inconsiderable portion of the chip surface of the semiconductor, which can be used for the optical and electronic components located on the semiconductor chip, such as the amplifier and drive unit as well as the optical transmitting and receiving elements. This previously known coupling therefore has, on the one hand, comparatively large dimensions and, on the other hand, the manufacturing costs for the coupling are correspondingly high, as these rise out of proportion with increasing chip surface. Moreover, it is not beneficial that the V-shaped receiver depressions cannot be integrated into a wafer at all or can be only poorly integrated with standard processes usual in chip manufacture. A further disadvantage of the coupling is that the optical conductors are clamped in between the walls of the V-shaped receiver depressions in order to fix the conductors axially in the receiver depression. Through the clamping force exerted here on the conductor, mechanical tensions can arise in the optical conductor, which can alter the optical properties of the conductor.
There thus exists an object of creating a coupling of the type mentioned at the outset, which has a compact construction as well as a mechanically stable connection between the coupling receiver and the coupling counterpart. Furthermore, there exists an object of providing a process, which allows a simple and economical manufacture of such a coupling.
This object is achieved, in relation to the coupling, by the coupling receiver having a stack of layers with at least two layers, by the receiver depression being arranged in the layer stack and extending transversely in relation to its layer planes over more than one layer, by the lateral boundary wall of the receiver depression, proceeding from the surface of the layer stack bordering on the receiver depression toward the interior of the receiver depression, having at least one cutback which is formed by a layer cutback in relation to an adjacent layer or a cutback layer region, and by the coupling counterpart having laterally at least one guide projection and/or locking projection (hereinafter simply xe2x80x9clocking projectionxe2x80x9d) which, in the coupling position, engages into the cutback of the micro-mechanical component.
The coupling counterpart is thus fixed form-locking in the receiver depression, avoiding clamping forces, whereby mechanical strains in the coupling receiver are avoided as far as possible. The coupling thereby permits a stable connection of its coupling elements. Since the receiver depression extends transverse to the layer planes of the layer stack, the receiver depression occupies only a comparatively small area of the surface of the coupling receiver, which makes possible correspondingly compact dimensions of the coupling. With a coupling receiver constructed as a semiconductor chip, chip surface can consequently be saved, which allows a correspondingly economical manufacture of the semiconductor chip. Moreover, in connection with the manufacture of the coupling, the receiver depression arranged in the layer stack enables a simple, layer by layer application of the cutback or cutbacks into the boundary wall of the receiver depression, whereby customary standard processes can be used in the micro-mechanics and/or semiconductor manufacture.
In one advantageous embodiment of the invention, it is provided that at least one cutback of the boundary wall is arranged between two layers and/or between two layer areas (hereinafter simply designated as xe2x80x9clayersxe2x80x9d) of the layer stack, offset in relation to each other transverse to the layer planes, and that at least one locking projection of the coupling counterpart, in the locking position, engages into the intermediate space formed between these layers. The coupling counterpart is then fixed in both its axial directions, namely in plug-in and extraction directions, by means of the locking projection, projecting in relation to the cutback, between the layers of the boundary wall arranged transverse to the layer planes of the layer stack on both sides of the cutback.
A bilateral axial fixation of the conductor on the boundary wall of the receiver can also be assured in that at least one layer arranged between two cutbacks forms a projection on the boundary wall, and in that, in the locking position of the coupling, transverse to the layering plane of this layer, respectively at least one locking projection of the coupling counterpart is arranged. With this embodiment of the invention, a projection of the boundary wall thus engages in a receiver of the coupling counterpart transverse to the layer planes of the layer stack restricted on both sides by locking projections.
In one embodiment of the invention, it is provided that the boundary wall of the receiver depression forms a laterally open sliding guide for the coupling counterpart, and that the coupling counterpart is moveable out of a pre-assembly position, in which the locking projection is out of engagement with the cutback of the micro-mechanical component, parallel to the layer planes of the layer stack, engaging with the locking projection into the cutback of the boundary wall. The coupling counterpart is then separably connectable with the micro-mechanical component by plugging in and retracting of the sliding guide.
In an especially advantageous embodiment of the invention, the coupling counterpart has on its exterior at least one resilient element which carries at least one stop projection on its exterior which, in operating position, engages into the cutback of the coupling receiver, whereby the stop projection in the coupling position of the coupling is directable against the restoring force of the resilient element from a locking position into an unlocking position. In this way, there results a plug-in coupling constructed as a stop connection which, by axially plugging the coupling elements into one another, or retracting them from one another, allows a simple and optionally separable joining of the coupling counterpart with the coupling receiver.
It is provided in connection with an especially advantageous embodiment of the invention that the coupling counterpart is constructed as the connection head of an optical and/or electrical conductor, and that the coupling receiver has at least one electrically and/or optically conducting element arranged in the receiver depression or bordering on it, which, in the coupling position of the coupling, stands in conducting connection with the optical and/or electrical conductor. The electrical and/or optical conductor here can be inserted into the receiver depression transverse in relation to the layer planes of the layer stack layers. Advantageously, in this way, for connecting the conductor with the coupling receiver situated, by way of example, on a micro-mechanical component, only a comparatively small area of the surface of the micro-mechanical component is required, so that the coupling can have correspondingly small dimensions.
With a coupling receiver which is part of a semiconductor chip, there thereby results a correspondingly small chip surface which allows an economical manufacture of the semiconductor chip. The receiver depression arranged in the layer stack enables in the manufacture of the connection, a simple, layer by layer installation of the cutback into the boundary wall of the receiver depression, whereby in micro-mechanics and/or semiconductor manufacture, customary standard processes are used. Since the optical and/or electrical conductor is joined in a form-locking manner with the coupling receiver, the conductor can be fixed in the receiver depression, while avoiding clamping forces. Mechanical tensions in the conductor, which can impair the optical characteristics of an optical conductor, are thereby avoided. It should be mentioned that the receiver depression can have a bottom which can serve, in the inserted position of the conductor, as a stop for the front face end of the conductor facing the micro-mechanical component.
It is advantageous if the resilient element having the stop projection is constructed as a spring tongue and/or as an annular jacket area of the connection head. An electrically and/or optically conducting core of the conductor engaging into the interior of the connection head can then, while retaining its cross section, be guided into the interior of the receiver depression and optionally up to its bottom, whereby the stop projection and the resilient element are arranged outside the core on the connection head. In this way, mechanical stresses in the core of the conductor are avoided to the greatest extent.
A preferred, especially advantageous embodiment of the invention provides that the electrically and/or optically conducting element of the coupling receiver, standing in conducting connection with the coupling counterpart engaging in the receiver depression, is formed by at least one electrically and/or optically conducting layer area bordering on the receiver depression, and that the coupling counterpart has at least one electrically and/or optically conducting area standing in conducting connection with the conductor which, in the coupling position of the coupling, is connected with the electrically and/or optically conducting layer of the layer stack in an electrically and/or optically conducting manner.
The coupling receiver can then, for example, be part of a micro-mechanical component, especially of a semiconductor chip. The electrically and/or optically conducting layer of the layer stack can then be connected with electrical and/or optical track conductors of the micro-mechanical component, which can be finished in a simple manner during the manufacture of the component by masking the electrically and/or optically conducting layer of the layer stack. Optionally, even several layers of the layer stack of the coupling receiver can be simultaneously connected with the conductor in an electrically and/or optically conducting manner. There thus results an especially low electrical and/or optical contact resistance between the coupling receiver and the conductor. Expediently, the conducting connection takes place through the resilient element of the coupling counterpart in that the resilient element is pressed, by the restoring force of its material in the operating position, on an electrically and/or optically conducting layer. Also, by this measure, an especially low electrical and/or optical contact resistance can be assured between the micro-mechanical component and the conductor. The compressive force can instead be generated, however, in that layer stack is made entirely or area-wise of an elastic material, and in that the end region of the conductor inserted or to be inserted into the receiver depression has a somewhat larger clear width than the receiver depth.
In an especially advantageous embodiment of the invention, it is provided that, in the coupling position of the coupling, the electrically and/or optically conducting element of the coupling receiver standing in conducting contact with the electrically and/or optically conductor is arranged on the bottom of the receiver depression facing the end face of the conductor, and is formed by an electrically and/or optically conducting layer situated on the bottom of the receiver depression. In this way, with an optical conductor, the optical radiation can be especially well transmitted between the coupling receiver and the conductor constructed, for example, as an optical fiber. On the bottom of the receiver depression an optical transmission element, for example a laser diode, and/or an optical receiving element, for example a photodiode or a photoelectric transmitter, can optionally be arranged.
In an especially advantageous embodiment of the invention, the conductor has an optically conductive core, which has a metal sheath on the outside. The sheath then serves, on the one hand, as a reflector to guide the optical radiation in the optically conductive core, and can, on the other hand, be used instead for transmitting electrical signals. Here, the core of the conductor engaging into the receiver depression can stand in conducting connection with an optically conductive element situated on the bottom of the receiver depression, and the metal sheath of the conductor can stand in conducting connection with at least one electrically conductive layer of the layer stack laterally bordering on the receiver depression. Consequently, there results a compactly constructed coupling for simultaneous transmission of electrical and optical signals.
In a further, advantageous embodiment of the invention, the coupling counterpart is a connection head of a tube or pipe conduit, wherein the tube or pipe conduit has at least one channel for a medium to be studied, which is connected with an opening situated on the coupling counterpart, wherein the opening of the coupling counterpart in the coupling position is sealed against the coupling receiver, and wherein at least one sensor for examining the medium situated in the channel is arranged on the bottom of the receiver depression of the coupling receiver in the area of the opening of the coupling counterpart. A chemically aggressive and/or electrically conductive medium, for example, can then be fed through the channel to the sensor situated on the coupling receiver. The coupling receiver and the sensor can, for example, be a part of a semiconductor chip or a micro-mechanical component. By the seal situated between the channel and the coupling receiver, the medium is screened from outside and especially also kept away from areas of the semiconductor chip or the micro-mechanical component on which the medium could cause corrosion and/or impair the electrical function of the semiconductor chip or the component.
With regard to the process for manufacturing the coupling of the invention, the above-mentioned objective is accomplished in that the receiver depression is introduced after positioning the layers into the layer stack. Thus, the individual layers are first stacked into a layer stack, and only then is the receiver depression introduced into the layers. The process has the advantage that it can be well integrated into the finishing process for manufacturing of a semiconductor forming the coupling receiver, especially a CMOS chip. The layer stack layers applied in the manufacture of the layer stack, for example to a substrate layer, can namely additionally also be used for the manufacture of other structures to be integrated into the semiconductor chip, for example printed circuits, transistors or optical sending and/or receiving elements, in that these layers are masked in the usual manner, for example by means of a photo-lithographic process.
Since the recess depression can only be introduced after finishing all layers necessary for the layer stack, the respective photo-resist layers required for the photo-lithographic manufacture of the additional structures can be applied to the individual layers installed throughout the layer stack, before the receiving depression is created in the layer stack. It is thereby avoided that the receiver depression prevents the spread of the photo-resist applied to the layers, for example in a spraying process, on the surface of the individual layers. Also, the formation of cracks, which can occur when applying a layer on an edge or an offset, is avoided by subsequent introduction of the recess depression into the layer stack.
It is advantageous if the layer stack is brought into contact with an etching agent for introducing the receiver depression, and if the layer materials of the individual layers of the layer stack are selected for molding a cutback into the boundary wall of the receiver depression, such that they have different etch rates with reference to the etching agent. The boundary wall of the receiver depression can then be manufactured simply by underetching the layers of the layer stack.